In operating a missile, it is required to secure high mobility at the terminal guidance. One approach is to use a multi-pulse rocket motor and activate an appropriate pulse at the terminal guidance to reaccelerate the missile. At the same time, it is often required to modify a trajectory of the missile by using a thruster.
A typical thruster has: a nozzle having a combustion gas exhaust hole; and an actuator that turns ON/OFF supply of combustion gas to the nozzle. A plurality of nozzles is arranged to arbitrary directions. The thruster performs trajectory control and attitude control for the missile by exhausting appropriate amount of combustion gas from a selected nozzle.
There are two methods for equipping the missile with the thruster. One is to fix the thruster to a combustion gas generator and equip the missile with the combustion gas generator (this type is hereinafter referred to as a separated thruster type). The other is to fix the thruster directly to a rocket motor (this type is hereinafter referred to as an unseparated thruster type).
In relation to the above, a two-pulse rocket motor is disclosed in Patent Literature 1 (Japanese Patent No. 4,719,182). The two-pulse rocket motor disclosed in Patent Literature 1 includes a second propellant loaded within a pressure vessel, a second igniter placed at an end surface of the second propellant, a barrier membrane disposed to cover both a whole of initial burning surface of the second propellant and the second igniter, and a first propellant loaded so as to cover a whole of the barrier membrane. Both the first propellant and the second propellant are formed in an internal-burning type propellant shape or an internal-end-burning type propellant shape. (Note that the internal-end-burning type is a type with which the inner surface burning and the end surface burning are occurred at the same time.) The barrier membrane includes an inner barrier membrane covering the inner surface of the second propellant and an aft barrier membrane covering the rear end surface of the second propellant. Respective ends of the aft barrier membrane and the inner barrier membrane are bonded with each other over an entire periphery.
Further, a multi-pulse rocket motor and a pulse unit thereof are disclosed in Patent Literature (Japanese Patent Publication JP-2012-255362). The pulse unit of the multi-pulse rocket motor disclosed in Patent Literature 2 has a structure with which it is possible to form a multi-pulse rocket motor of 3-pulse or more. The pulse unit includes a propellant loaded within a pressure vessel and formed in an internal-burning type propellant shape or an internal-end-burning type propellant shape, an igniter placed at an end surface of the propellant, a barrier membrane disposed to cover both a whole of initial burning surface of the propellant and the igniter, a forward joint arranged at a forward end of the pressure vessel, and a rearward joint arranged at a rearward end of the pressure vessel. The forward joint is formed so as to be connectable with a rearward joint of another pulse unit. On the other hand, the rearward joint is formed so as to be connectable with a forward joint of still another pulse unit.
Moreover, a combustion gas supply control device is disclosed in Patent Literature 3 (Japanese Patent Publication JP-2013-024034). The combustion gas supply control device disclosed in Patent Literature 3 is a device which can supply combustion gas to a selected combustion gas exhaust hole at a desired timing, in a combustion gas generator such as an unseparated thruster type multi-pulse rocket motor. The combustion gas supply control device includes a pressure vessel, a first propellant loaded within the pressure vessel to be burned at a first pulse, a second propellant loaded within the pressure vessel to be burned at a second pulse subsequent to the first pulse, a front motor head fixed to a front portion of the pressure vessel and having a combustion gas exhaust hole, and a rear motor head fixed to a rear portion of the pressure vessel and having a combustion gas exhaust hole. The combustion gas supply control device prevents combustion gas of the first propellant at the first pulse from flowing into the combustion gas exhaust hole of the front motor head and supplies combustion gas of the second propellant at the second pulse to the combustion gas exhaust hole of the front motor head.
By the way, in order to realize, for example, a three-pulse gas generator, three propellants corresponding to three pulses, respectively should be loaded in a pressure vessel of a limited size. In this case, it is necessary to consider an arrangement of the three propellants in the pressure vessel. Three propellants should be supported in the pressure vessel by some means. It is necessary to consider how to support the three propellants in order to burn the three propellants at a different timing.
Further, power of force obtained by combustion of the propellant depends on a burning area. Therefore, it is necessary to consider an arrangement of the propellants such that a sufficient burning area is secured in order to obtain desired power of force. However, it is difficult to arrange the propellants to secure the sufficient burning area in a limited space.